Donald - I was having problems with my XYZ50 - was getting harder to start and then would not start. Took the carb apart and I found lots of garbage in the two internal screens. (I was new to gassers and forgot to install a fuel filter). Also one of the the diaphragm's stop-valve flaps was a little raised. I ordered and installed a new diaphragm, no difference. But I had also had plugged the choke plate hole with a small bolt and nut, and used lock-tight on that, and I think that lock-tight may have flowed into some places that it shouldn't. (In hindsight I should have removed the plate before putting the bolt in). I soaked the carb in Acetone, but still had problems.

So I ended up getting a replacement carb from Hobby City (only $30), and the engine runs like a top now.